Cameras are increasingly used to remotely monitor and inspect areas by capturing still and moving images of the areas. For example, cameras are ubiquitous at airports, hospitals, government offices, commercial stores, roadways, and parking lots to monitor and record events in the areas. Cameras are also often employed to initially inspect areas of unknown hazards to reduce personnel exposure to unknown hazardous conditions.
When high-energy photons are present in the vicinity of the camera, the high-energy photons (i.e., x-rays, or gamma rays) may directly interact with a sensor in the camera to produce a visible speckle effect (e.g., white spots) in the video images. These white spots or “specks” are caused by the high-energy photons interacting with the sensor to create a large number of electron-hole pairs in a localized region nominally the size of a single pixel. This may result in that pixel becoming saturated, i.e., reaching the maximum intensity or maximum charge collection capacity, thus creating the visible speckle effect in the video image. The number of affected pixels is generally proportional to the flux rate (photons per unit area per unit time) of high energy photons at the camera location.
The speckle effect in the video image caused by high-energy photons has been observed for years and is generally considered undesirable noise in the recorded video image. Algorithms have been written by the present inventors as well as others to remove and discard the unwanted “specks” from images to improve image quality. These same algorithms form the basis for software to detect and count the specks for radiation detection and measurement purposes. For example, U.S. Pat. No. 7,391,028 and its progeny describe an apparatus and method for detecting radiation that utilizes pixelated image detectors, such as those included in conventional video cameras, camera phones, webcams, netcams, security cameras, traffic cameras, or any combination of these. The actual test results described therein all use a camera that has been covered with a thick black cloth, black tape, or other means to block the visible light, thereby reducing or preventing the visible light from interacting with the sensor in the camera. The resulting speckle effect of the covered camera is attributed to high-energy photons from a test source and analyzed to determine the presence and/or flux rate from the radioisotope or RGD at the camera location.
Other applications of varying sensitivity have been developed to utilize existing cameras to detect and/or quantify high-energy photons based on the speckle effect. However, each application consistently requires some filter or cover over the camera lens to reduce or prevent the visible light from interacting with the sensor. In doing so, the existing systems and methods effectively prevent the camera from performing its original purpose—i.e., to capture still or video images.
Therefore, a system and method that can utilize existing cameras to detect and/or quantify high-energy photons while simultaneously allowing the camera to capture still or video images would be useful. For example, government organizations, law enforcement agencies, and security personnel may use existing video cameras already installed in various locations to detect and/or quantify radioisotope levels in the areas while still obtaining still or video images from the camera.